Robot contestants in the second annual Defense Advanced Research Projects Agency (Darpa) Grand Challenge race are gearing up for battle up on Sunday in the Mojave Desert as organisers hope for an improvement on last year's fiasco.

After two weeks of trials the 43 original contenders have been whittled down to 23 teams hoping to win the $2m prize for traversing a rugged desert route with no human intervention. 

In last year's race no team got further than eight miles of the 155 mile course before crashing.

"In 2004 we thought it was quite an achievement that a robot was able to go about seven and a half miles," said Darpa director Dr Tony Tether.

"But the results of this National Qualification Event tell me that we will leave that in the dust of the Mojave!"

Stanford University's team, which is using a diesel-powered Volkswagen Touareg R5 loaded with six blade servers, claims to have performed flawlessly in the time trials by using a mix of laser guided navigation and a computer image monitoring system designed by a volunteer Intel engineer.

The course will only be revealed to competitors two hours before the start of the race.

Last year common problems included cars that were unable to function under bridges due to the lack of a GPS signal, and vision systems that could not 'see' barbed wire.

"We established the Grand Challenge to foster the development of autonomous vehicle technology that will some day save the lives of Americans protecting our country on the battlefield," said Grand Challenge programme manager Ron Kurjanowicz.

The project is being funded by Darpa with the ultimate goal of making one of three ground military forces automated by 2015.